Effect of ligand substitution in pyrazolone based binary and ternary Cu(II) complexes on DNA binding, protein binding and anti-cancer activity on A549 lung carcinoma cell lines

A new series of 4-acyl pyrazolone based ternary Cu(II) complexes [Cu(TPMP)(Phen)NCS] (1), [Cu(TPMP)(Bipy)NCS] (2) and binary Cu(II) complex [Cu(TPMP-BA)(2)] (3) has been synthesized and characterized by structural, analytical and spectral methods, in order to investigate the influence of ligand substitution on structure and pharmacological properties. In all of the complexes, the pyrazolone based ligand is coordinated to the Cu(II) ion in a neutral fashion as bidentate ligand. The single-crystal X-ray study of binary complex (3) exhibits a square planar structure, while ternary complexes (1) and (2) revealed slightly distorted square-pyramidal structures. The interaction of the compounds with calf thymus DNA (CT-DNA) has been explored by absorption and emission titration methods, which revealed that compounds 1-3 could interact with CT-DNA through intercalation. The interaction of the compounds with bovine serum albumin (BSA) was also investigated using fluorescence spectroscopic method. The results indicated that all of the compounds could quench the intrinsic fluorescence of BSA in a static quenching process. Further, the cytotoxic effect of the compounds 1-3 examined on human lung cancerous cell line (A549) and noncancerous rat cardiomyoblasts (H9C2) cell lines showed that all three complexes exhibited substantial cytotoxic activity. All the pharmacological investigations support the fact that there exists a strong influence of ligand substitution on pharmacological activities. (C) 2014 Elsevier Ltd. All rights reserved.